Abstract: :
Purpose: An absolute indication for treatment of toxoplasmaretinochoroiditis (TR) is the presence of lesions within onedisc diameter of the optic nerve head, based on the assumptionthat these would lead to full thickness retinal loss with aresulting absolute scotoma breaking out to the periphery. Wesought to test this assumption.Methods: A cross–sectional observational study of unselectedcases of TR. Each affected eye had automated central visualfield testing when their disease was quiescent.Results: 65 eyes were studied. 16 (24.6%) were excluded dueto low quality (greater than 33% fixation losses, 20% falsepositives or 20% false negatives). Of the remaining 49 eyes,47 eyes had a demonstrable central field defect; absolute defectswere seen in 29 eyes (61.7%), of which 16 (55.2%) showed breakout to the periphery, the remaining 13 (44.9%) remaining confinedto the lesion. Relative field defects were detected in 18 (38.3%)eyes. For scars lying within 1 DD of the disc (n=9), 7/9 hadan absolute defect with peripheral breakout; by contrast, oflesions outside this zone (n=40) an absolute defect with breakoutwas seen in 9 (p=0.02), without breakout in12, a relative defectin 17 and no defect in 2.Conclusions: This study supports the hypothesis that scars dueto TR adjacent to the optic disc are significantly associatedwith absolute defects breaking out to the periphery comparedto those lying outside this area. Whether treatment of theselesions affects the resulting field loss remains to be provenby clinical trial.